1. Field of the Invention
The invention relates to a membrane structure applied to or across the ostium of an atrial appendage for filtering blood between an atrium of the heart and the associated atrial appendage or appendages to prevent a thrombus from leaving the atrial appendage while allowing blood flow through the membrane.
2. Description of the Related Art
There are a number of heart diseases (e.g., coronary artery disease, mitral valve disease) that have various adverse effects on the heart. An adverse effect of certain cardiac diseases, such as mitral valve disease, is atrial (or auricular) fibrillation. Atrial fibrillation may result in pooling of blood in the left atrial appendage. Blood pooling may also be spontaneous. When blood pools in the atrial appendage, blood clots can form and accumulate therein, build upon themselves, and propagate out from the atrial appendage into the atrium. These blood clots can then enter the systemic or pulmonary circulations and cause serious problems if they migrate from the atrial appendage and become free in the blood stream and embolize distally into the arterial system. Similar problems also occur when a blood clot extending from an atrial appendage into an atrium breaks off and enters the blood supply. Since blood from the left atrium and ventricle supply the heart and brain, blood clots from the atrial appendages can obstruct blood flow therein causing heart attacks, strokes or other organ ischemia. It is therefore necessary to find a means of preventing blood clots from forming in the atrial appendages and to prevent these blood clots, once formed, from leaving the atrial appendages to the heart, lungs, brain or other circulations of the patient which can cause heart attacks or strokes or other organ ischemia.
U.S. Pat. 5,865,791 relates to the reduction of regions of blood stasis and ultimately thrombus formation in such regions, particularly in the atrial appendages of patients with atrial fibrillation. More specifically, the ""791 patent relates to procedures and devices for affixing the atrial appendages in an orientation that prevents subsequent formation of thrombus. In the ""791 patent, the appendage is removed from the atrium by pulling on it and by putting a loop around it to form a sack of the atrial appendage and then cutting it off from the rest of the heart.
U.S. Pat. No. 5,306,234 relates to a method for surgically closing the passage between the atrium and the atrial appendage or severing the atrial appendage.
Other methods of treatment include surgically removing the atrial appendages to prevent blood stasis in the atrial appendages.
The invention provides a filtering membrane that allows blood to pass therethrough while substantially preventing blood clots formed in the atrial appendages from exiting therefrom. Such clots may cause heart attacks, strokes and other embolic events if allowed to leave the atrial appendage and enter the bloodstream.
The filtering membrane is permanently positioned across the ostium of the atrial appendage by a support structure attached to the filtering membrane. The filtering membrane filters blood flowing between the atrium and the left atrial appendage and effectively isolates blood clots from leaving the atrial appendage and entering the atrium. It may be larger than the ostium of the appendage, and extend over an area larger than the appendage ostium. It is percutaneously delivered to the ostium of the atrial appendage by a catheter and then may be expanded for positioning across or over the ostium and has a means to secure the filtering membrane across or over the ostium.
The filtering membrane itself is permeable to permit blood flow across the membrane. By allowing the such blood flow across the membrane, the porous structure minimizes any pressure gradient between the atrial appendage and the atrium in a controlled manner.
The porous filtering membrane may eventually become infiltrated with cells. The permeable filtering membrane allows such tissue growth which may begin along the outer periphery of the structure. Such tissue growth minimizes uncontrolled leakage about the periphery of the filtering membrane and may assist in attachment of the filtering membrane to the ostium or surrounding tissue.
There are many means for fixing the filtering membrane in position across the ostium of the atrial appendage. The support structure for the filtering membrane may have a means for self-centering the filtering membrane over the appendage ostium. The filtering membrane may be glued to the wall of the atrial appendage adjacent the ostium, or the support structure may have wires, barbs, prongs or other methods of fixation which pass through the ostium and extend into or through the atrial appendage and which permanently engage an interior wall thereof. Alternatively, an anchor in the wall of the atrial appendage may be tethered to the filtering membrane for holding the filtering membrane in place. Springs may also extend between the anchor and the filtering membrane to hold the filtering membrane against the ostium. The filtering membrane may also be connected to a tether, elastic tether or spring and placed through the atrial appendage wall for holding the filtering membrane against the ostium and may pull on the atrial appendage such that its volume is reduced or eliminated, trapping and isolating blood clots therein.
Part of the device may involve a suction apparatus to remove clots that are already in place. The filtering membrane placement may require closure of an atrial septal defect created by the placement of this filter device about the appendage.
Alternatively, the filtering membrane may be held in place by a coiled spring which engages the interior wall of the atrial appendage.
The filtering membrane itself is permeable. The permeability of the filtering membrane allows blood to flow across, while inhibiting blood clots within the atrial appendage from exiting the atrial appendage into the bloodstream. In the case of a permeable filtering membrane, it may eventually become infiltrated with cells so that it may become a xe2x80x9clivingxe2x80x9d structure, and can develop an endothelial/endocardial lining to enable it in turn to become a non-thrombogenic surface. It thus can develop an endothelium and with time become highly biocompatible. It may be coated or covered with an anticoagulant or other compounds, such as, for example, heparin, or it may be treated to prevent thrombus from forming on the filtering membrane surface, to extend its patency or until it is infiltrated with cells and/or develops an endothelial covering.
The device, when implanted in the atrial appendage, may also have the ability to perform electrical monitoring of the heart. This may include two or more electrical contacts placed apart on the device, and connected to signal conditioning circuitry for determination of cardiac features such as rhythm of the atria or ventricles. Another sensor on the device could measure pressure of the atria, atrial appendage, or ventricular end diastolic pressures (left or right) through the open mitral or tricuspid valves. A suitable telemetry system would be used to telemeter this important electrical and hemodynamic information non-invasively outside the patient. Also, memory could be present on the device in order to record the information for later recovery via noninvasive telemetry.
It is an object of the invention to provide a filter between the atrium and atrial appendage to prevent blood clots from flowing therebetween.
It is an object of the invention to provide a filter between the atrium and atrial appendage to allow blood flow across the filter, e.g., to reduce any hemodynamic pressure differential therebetween.
It is an object of the invention to provide a filter which is permanently implanted between the atrium and the atrial appendage by a support structure which substantially conforms to the contours of the ostium and the interior wall of the atrial appendage.
It is an object of the invention to reduce the volume of an atrial appendage to reduce the size of the region for potential blood stasis formation, and consequently the effective volume of the affected atrium.
It is an object of the invention to reduce the region of static blood in the atrial appendages and hence the thrombogenicity of the atrium.
It is an object of the invention to measure hemodynamics pressure (or flow), or electrical signals in the heart and telemeter them outside the body for diagnosis or monitoring.
It is an object of the invention to prevent blood clots from forming in the atrial appendages.
It is an object of the invention to position across the ostium of the atrial appendage a non-thrombogenic, biocompatible surface that prevents blood clots from forming.
It is an object of the invention to provide a permeable filtering membrane surface which may eventually become lined with endothelial or endocardial cells.
It is an object of the invention to isolate the atrial appendage from the atrium proper with respect to the passage of thrombus with a filtering membrane, while allowing communication through which blood may flow.
It is an object of the invention to minimally invasively prevent blood clots from forming in the atrial appendages and escaping therefrom.
It is an object of the invention to remove thrombi from the atrium via suction or other means.
It is an object of the invention to prevent thrombus by use of heparin, other antithrombogenic substances, or other compounds on or eluted from the filtering membrane.
It is an object of the invention to ensure the filtering membrane is centered across or over the ostium of the atrial appendage.
It is an object of the invention to accurately place the filtering membrane across or over the ostium of the atrial appendage.